Marinova Maya, Pascal Simon, Guénée Laure, Besnard Céline, Shivachev Boris, Kostova Kalina, Villani Claudio, Franzini Roberta, Dimitrov Vladimir, Lacour Jérôme
Department of Organic Chemistry, University of Geneva, Quai Ernest Ansermet 30, CH-1211 Geneva 4, Switzerland.
Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. 9, Sofia 1113, Bulgaria.
J Org Chem. 2020 Sep 18;85(18):11908-11923. doi: 10.1021/acs.joc.0c01716. Epub 2020 Sep 10.
A straightforward approach to the synthesis of two different series of cationic [5]helicenes has been achieved including, in dioxa series, the possibility to introduce aromatic functional groups at the periphery of the helical structure. While photophysical study highlights that the introduction of aryl substituents at position 23 of the helical moieties has a negligible impact on the optical properties, styryl substituents allow a welcoming extension of the conjugation pathways. Finally, a red shift of the optical properties was evidenced upon introduction of nitrogen atoms in the helicene scaffold, leading to particularly good fluorescence efficiencies in the red domain for a helicenic dye. Detailed information on racemization kinetics was collected for the most stable species upon direct high-performance liquid chromatography (HPLC) resolution or, when configurational lability was too high, through VT-HPLC analysis on the chiral stationary phase (Δ values ranging from 85.0 to 137.1 kJ·mol and above).
已经实现了一种合成两种不同系列阳离子[5]螺旋烯的直接方法，在二氧杂系列中，包括在螺旋结构外围引入芳香族官能团的可能性。虽然光物理研究表明在螺旋部分的23位引入芳基取代基对光学性质的影响可忽略不计，但苯乙烯基取代基能使共轭途径得到有利的扩展。最后，在螺旋烯支架中引入氮原子后，光学性质出现红移，这使得一种螺旋烯染料在红色区域具有特别好的荧光效率。通过直接高效液相色谱（HPLC）拆分，或在构型不稳定性过高时，通过在手性固定相上进行变温HPLC分析（Δ值范围为85.0至137.1 kJ·mol及以上），收集了最稳定物种的外消旋动力学详细信息。
